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Ball milling is a feasible and promising method of biochar modification that can significantly increase its adsorption ability to methylene blue (MB). This study synthesized nine biochars derived from water hyacinth under different pyrolysis temperatures and modified with ball milling and Fe3O4. The structural properties of the pristine and ball-milled magnetic biochars were investigated and employed to adsorb MB. The results showed that ball milling significantly enhanced the specific surface area, total pore volume, and C-, N-, and O-containing groups of biochars, especially in low-temperature pyrolysis biochars. The Langmuir isotherm and the pseudo-secondary kinetic model fitted well with the MB adsorption process on biochars. After ball-milled magnetic modification, the adsorption capacity of biochar at 350 °C for MB was increased to 244.6 mg g−1 (8-fold increase), owing to an increase in accessible functional groups. MB removal efficiencies by low-temperature pyrolysis biochars were easily affected by pH, whereas high-temperature pyrolysis biochars could effectively remove MB in a wide pH range. WQM1, with the high adsorption capacity and stability, provided the potential to serve as an adsorbent for MB removal. Based on DFT calculations, the chemisorption and electrostatic interactions were the primary mechanism for enhancing MB removal with ball-milled magnetic biochar at low-temperature pyrolysis, followed by H-bonding, π–π interaction, hydrophobic interaction, and pore filling. [ABSTRACT FROM AUTHOR]

In this work, a novel xonotlite nanocomposite was synthesised with abandoned eggshell by hydrothermal method, and organic-modified with toluene diisocyanate (TDI) for the removal of Pb(II) and Cd(II) from wastewater. The xonotlite and organic-modified xonotlite were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunner-Emmet-Teller (BET) and Fourier transform infrared spectroscopy (FTIR) methods. The effect of solution pH, contact time, adsorbent dose, and initial concentrations were also investigated. The organic-modified xonotlite was found to have a high loading capacity of 467.7 mg g−1 for Pb(II) and 147.6 mg g−1 for Cd(II). The adsorption of Pb (II) and Cd (II) was well fitted by Freundlich model and pseudo-second order model. In the effect of the competing ion, the ions like Na(I) and K(I), had little effect on the Pb(II) and Cd(II) removal efficiency. Furthermore, the organic-modified xonotlite can be reused and shown good recyclability. It was concluded that the organic-modified xonotlite is simple, fast and effective adsorbent for the removal of Pb(II) and Cd(II) in treating wastewater with outstanding adsorption capacity. [ABSTRACT FROM AUTHOR]

The mechanisms of low cadmium (Cd) accumulation in sweet potato cultivars are obscure. In this study, seedlings of a low-Cd (Nan88, N88) and a high-Cd cultivar (Xiang 16, X16) were grown in Hoagland’s solution containing Cd concentrations of 0 (control), 1 (Cd1), and 10 µM (Cd10) for 20 days. We analyzed the Cd accumulation, root morphology and low molecular weight organic acids (LMWOAs) excreted by the root tips (RTs). The total root length (RL) and specific root length (SRL) in X16 were greater than those in N88 following Cd treatments. In the Cd1treatment, RL and surface area for root diameter was ≤0.2 mm, and RTs in X16 were also greater than those in N88. LMWOAs excreted from the RTs initially increased and then decreased as Cd concentration increased. The RTs of N88 were more efficient at excreting organic acids than were those of X16. The low-Cd cultivar with lower RL and SRL displayed greater ability to excrete organic acids in Cd treatments, which can decrease Cd translocation from roots to shoots. Furthermore, root morphology and some LMWOAs released from the root tips played an important role in the differing rates of Cd accumulation in the two sweet potato cultivars. [ABSTRACT FROM PUBLISHER]